The processing of semiconductor wafers and substrates is very sensitive to problems of contamination. This is also true with photomasks, flat panel displays, data disks, and other articles relating to the semiconductor industry. These articles require extremely low contamination levels. Even minute contaminants can cause defects to occur in the processing of these low-contamination wafer articles. Accordingly, it is necessary to maintain a high level of cleanliness during all or nearly all stages of production.
Semiconductor wafers, substrates, photomasks, flat panel displays and other similar low-contamination wafer products are also typically processed in batches. Batch handling may occur throughout the entire production process, or for one or more processing steps or related handling operations. Batch processing of this type almost always utilizes some type of carrier or carriers to hold the thin wafer-like materials being processed.
In the batch processing of semiconductor substrates and wafers, a wafer carrier is used to hold a group of these articles. The wafer carriers can be of various designs and are more specifically referred to as a wafer boat. In many applications the wafer boat is made of a suitable polymeric material, e.g. polypropylene or TEFLON.RTM. fluoropolymer. The sides and sometimes the bottom of the wafer boat have receiving slots formed to receive and positionally restrain the wafers in a spaced array with the faces of the wafers adjacent one another. Typically, the central axes of the wafers are aligned. The wafers are slid into the boat, such as from the side or above and removed by sliding them outwardly. The receiving slots in the wafer boat are shallow so that the wafer is engaged only at the peripheral edges and along a thin marginal band extending inwardly from the periphery.
Wafer carriers can also be provided in the form of a protective case or box in which the wafers are held and enclosed against contamination during travel within the processing facility. Wafer carriers of this type are frequently designed to hold a wafer boat having a complementary design. The complementary relationship of the protective wafer carrier box and the wafer carrier boat allow the boat and supported wafers to be fully enclosed and positionally restrained in all directions during transport.
The manufacture of wafer carriers also includes their cleaning. Cleaning of wafer carrying boxes and wafer carrying boats is difficult because they typically have features which include slots, grooves or apertures which are difficult to fully clean. This is greatly exacerbated by the extremely low contamination levels which can be accepted for articles used directly or indirectly in processing of the wafer articles. Dust, metal particles, oils and other organic chemicals may be present on the surfaces of the molds or other production tools used to make wafer carriers. Fully cleaning the wafer carriers to the required extremely low contamination levels is also difficult. Cleaning the wafer carriers for use in semiconductor processing is a task which in some cases is almost as difficult as mechanically forming the article.
The cleaning of wafer carriers has until this invention remained a difficult and relatively costly procedure. The current invention has several advantages and benefits which are explained or otherwise indicated herein.